Nitride Semiconductor Light Emitting Device and Fabrication Method Thereof

ABSTRACT

A nitride semiconductor light-emitting device according to the present invention comprises a first nitride semiconductor layer; an active layer formed on the first nitride semiconductor layer; a second nitride semiconductor layer formed on the active layer; and a third nitride semiconductor layer having AlIn, which is formed on the second nitride semiconductor layer. And a nitride semiconductor light-emitting device comprises a first nitride semiconductor layer; an n-AlInN cladding layer formed on the first nitride semiconductor layer; an n-InGaN layer formed on the n-AlInN cladding layer; an active layer formed on the n-InGaN layer; a p-InGaN layer formed on the active layer; a p-AlInN cladding layer formed on the p-InGaN layer; and a second nitride semiconductor layer formed on the p-AlInN cladding layer.

TECHNICAL FIELD

The present invention relates to a nitride semiconductor light-emittingdevice and fabrication method thereof.

BACKGROUND ART

Generally, GaN-based nitride semiconductors find its application fieldsin electronic devices (i.e., high-speed switching and high outputdevices) such as optical devices of blue/green LED (Light EmittingDiode), MESFET (Metal Semiconductor Field Effect Transistor) and HEMT(High Electron Mobility Transistors).

The GaN based nitride semiconductor light emitting device is grown on asapphire substrate or a SiC substrate. Then, an Al_(Y)Ga_(1-Y)Npolycrystalline thin film is grown on the sapphire substrate or the SiCsubstrate as a buffer layer at a low growth temperature. Then, anundoped GaN layer, a Si-doped n-GaN layer, or a mixture of the above twostructures is grown on the buffer layer at a high temperature to form ann-GaN layer. Also, a Mg-doped p-GaN layer is formed at upper layer tomanufacture a nitride semiconductor light emitting device. An emissionlayer (a multiple quantum well structure activation layer) is interposedbetween the n-GaN layer and the p-GaN layer.

A related art p-GaN layer is formed by doping Mg atoms while growingcrystal. It is required that Mg atoms implanted as a doping sourceduring crystalline growth be substituted by Ga location and thus serveas a p-GaN layer. The Mg atoms are combined with a hydrogen gasdissolved in a carrier gas and a source to form a Mg—H complex in a GaNcrystalline layer, resulting in a high resistant material of about 10

.

Accordingly, after a pn junction light-emitting device is formed, thereis an need for a subsequent activation process for cutting the Mg—Hcomplex and substituting the Mg atoms at the Ga location. However, inthe light-emitting device, the amount of carriers contributing to lightemission in the activation process is about 10¹⁷/

, which is very lower than the Mg atomic concentration of 10¹⁹/

or higher. Accordingly, there is a disadvantage in that it is verydifficult to form a resistive contact.

Furthermore, the Mg atoms remaining within the p-GaN nitridesemiconductor without being activated as carriers serve as the center atwhich light emitted from the interface with the active layer is trapped,abruptly decreasing the optical output. In order to improve thisproblem, a method in which contact resistance is lowered to increasecurrent injection efficiency using a very thin transparent resistivemetal material has been employed.

However, the thin transparent resistive metal used to decrease thecontact resistance is about 75 to 80% in optical transmittance. Theremaining optical transmittance serves as loss. More particularly, thereis a limit to reducing an operating voltage due to high contactresistance.

DISCLOSURE OF INVENTION

Technical Problem

An object of the present invention is to provide a nitride semiconductorlight-emitting device and fabrication method thereof, wherein thecrystallinity of an active layer constituting the nitride semiconductorlight-emitting device can be improved and the optical output andreliability can be improved.

Technical Solution

In order to accomplish the above object, a first embodiment of a nitridesemiconductor light-emitting device according to the present inventioncomprises a first nitride semiconductor layer; an active layer formed onthe first nitride semiconductor layer; a second nitride semiconductorlayer formed on the active layer; and a third nitride semiconductorlayer having AlIn, which is formed on the second nitride semiconductorlayer.

Furthermore, in order to accomplish the above object, a secondembodiment of a nitride semiconductor light-emitting device according tothe present invention comprises a substrate; a buffer layer forming onthe substrate; a first GaN based layer into which In is doped, the firstGaN based layer being formed on the buffer layer; a second GaN basedlayer into which Si and In are doped, the second GaN based layer beingformed on the first GaN based layer; an In_(X)Ga_(1-X)N layer formed onthe second GaN based layer; an active layer formed on theIn_(X)Ga_(1-X)N layer; a p-GaN based layer formed on the active layer;and an n-AlInN layer or a p-AlInN layer formed on the p-GaN based layer.

Furthermore, in order to accomplish the above object, a third embodimentof a nitride semiconductor light-emitting device according to thepresent invention comprises a first nitride semiconductor layer; ann-AlInN cladding layer formed on the first nitride semiconductor layer;an n-InGaN layer formed on the n-AlInN cladding layer; an active layerformed on the n-InGaN layer; a p-InGaN layer formed on the active layer;a p-AlInN cladding layer formed on the p-InGaN layer; and a secondnitride semiconductor layer formed on the p-AlInN cladding layer.

Furthermore, in order to accomplish the above object, a fourthembodiment of a nitride semiconductor light-emitting device according tothe present invention comprises a first nitride semiconductor layer; ann-AlInN cladding layer formed on the first nitride semiconductor layer;an active layer formed on the n-AlInN cladding layer; a p-AlInN claddinglayer formed on the active layer; and a second nitride semiconductorlayer formed on the p-AlInN cladding layer.

Furthermore, in order to accomplish the above object, a fifth embodimentof a nitride semiconductor light-emitting device according to thepresent invention comprises a first nitride semiconductor layer; anactive layer formed on the first nitride semiconductor layer; a p-InGaNlayer formed on the active layer; a p-AlInN cladding layer formed on thep-InGaN layer; and a second nitride semiconductor layer formed on thep-AlInN cladding layer.

Furthermore, in order to accomplish the above object, a first embodimentof a method of fabricating a nitride semiconductor light-emitting deviceaccording to the present invention comprises: forming a buffer layer ona substrate; forming a GaN based layer on the buffer layer; forming afirst electrode layer on the GaN based layer; forming an InxGa_(1-X)Nlayer on the first electrode layer; forming an active layer on theInxGa_(X)N layer; forming a p-GaN based layer on the active layer; andforming an n-AlInN layer or a p-AlInN layer on the p-GaN based layer.

Furthermore, in order to accomplish the above object, a secondembodiment of a method of fabricating a nitride semiconductorlight-emitting device according to the present invention comprises:forming a buffer layer on a substrate; forming an In-doped GaN basedlayer into which indium (In) is doped on the buffer layer; forming afirst electrode layer on the In-doped GaN based layer; forming ann-AlInN cladding layer on the first electrode layer; forming an activelayer on the n-AlInN cladding layer; forming a p-AlInN cladding layer onthe active layer; forming a p-GaN based layer on the p-AlInN claddinglayer; and forming a second electrode layer on the p-GaN based layer.

Furthermore, in order to accomplish the above object, a third embodimentof a method of fabricating a nitride semiconductor light-emitting deviceaccording to the present invention comprises: forming a buffer layer ona substrate; forming an In-doped GaN based layer into which indium (In)is doped on the buffer layer; forming a first electrode layer on theIn-doped GaN based layer; forming an active layer that emits light onthe first electrode layer; forming a p-InGaN layer on the active layer;forming a p-AlInN cladding layer on the p-InGaN layer; forming a p-GaNbased layer on the p-AlInN cladding layer; and forming a secondelectrode layer on the p-GaN based layer.

Advantageous Effects

According to the present invention, the crystallinity of an active layerconstituting a nitride semiconductor light-emitting device can beimproved and the optical output and reliability can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view schematically showing the stack structure of a nitridesemiconductor light-emitting device according to a first embodiment ofthe present invention.

FIG. 2 is a view schematically showing the stack structure of a nitridesemiconductor light-emitting device according to a second embodiment ofthe present invention.

FIG. 3 is a view schematically showing the stack structure of a nitridesemiconductor light-emitting device according to a third embodiment ofthe present invention.

FIG. 4 is a view schematically showing the stack structure of a nitridesemiconductor light-emitting device according to a fourth embodiment ofthe present invention.

FIG. 5 is a view schematically showing the stack structure of a nitridesemiconductor light-emitting device according to a fifth embodiment ofthe present invention.

FIG. 6 is a view schematically showing the stack structure of a nitridesemiconductor light-emitting device according to a sixth embodiment ofthe present invention.

FIG. 7 is a view schematically showing the stack structure of a nitridesemiconductor light-emitting device according to a seventh embodiment ofthe present invention.

FIG. 8 is a view schematically showing the stack structure of a nitridesemiconductor light-emitting device according to an eighth embodiment ofthe present invention.

FIG. 9 is a view schematically showing the stack structure of a nitridesemiconductor light-emitting device according to a ninth embodiment ofthe present invention.

FIG. 10 is a view schematically showing the stack structure of a nitridesemiconductor light-emitting device according to a tenth embodiment ofthe present invention.

FIG. 11 is a view schematically showing the stack structure of a nitridesemiconductor light-emitting device according to an eleventh embodimentof the present invention.

MODE FOR THE INVENTION

The present invention will be described in detail below in connectionwith embodiments with reference to the accompanying drawings.

FIG. 1 is a view schematically showing the stack structure of a nitridesemiconductor light-emitting device according to a first embodiment ofthe present invention.

A nitride semiconductor light-emitting device 1 according to the presentinvention includes a buffer layer 4 formed on a substrate 2, as shown inFIG. 1. In this case, the buffer layer 4 can have one of an AlInN/GaNstack structure, an InGaN/GaN supper lattice structure, anIn_(X)Ga_(1-X)N/GaN stack structure, anAl_(X)In_(Y)Ga_(1-(X+Y))N/In_(X)Ga_(1-X) N/GaN stack structure(0≦x≦1,0≦y≦1, x+y≦1).

An In-doped GaN layer 6 into which indium is doped is then formed on thebuffer layer 4. A n-type first electrode layer is formed on the In-dopedGaN layer 6. In this case, a Si-In co-doped GaN layer 8 into whichsilicon and indium are doped at the same time can be adopted as then-type first electrode layer.

An In_(X)Ga_(1-X)N layer 10 having a low content of indium is alsoformed on the Si-In co-doped GaN layer 8. An active layer 12 foremitting light is formed on the InxGa_(1-x)N layer 10. The active layer12 can have a single quantum well structure or a multi quantum wellstructure formed as an InGaN well layer/InGaN barrier layer. An exampleof the stack structure will be described in more detail with referenceto FIG. 3 later on.

A p-GaN layer 14 is then formed on the active layer 12. At this time,the p-GaN layer 14 may be formed so that it may be doped with magnesium.

A n-type second electrode layer is then formed on the p-GaN layer 14. Inthis case, an n-AlInN layer 16 may be adopted as the n-type secondelectrode layer. At this time, the n-AlInN layer 16 may be formed sothat it may be doped with silicon.

In the nitride semiconductor light-emitting device according to thepresent invention, the Si—In co-doped GaN layer 8 (i.e., the firstelectrode layer) and the n-AlInN layer 16 (i.e., the second electrodelayer) are all formed using n-type nitride and the p-GaN layer 14 isformed between the Si-In co-doped GaN layer 8 and the n-AlInN layer 16.In view of the above, it can be considered that the nitridesemiconductor light-emitting device according to the present inventionhas an n/p/n junction light-emitting device structure unlike the relatedart p/n junction light-emitting device.

As described above, the present invention can provide a scheme in whicha low carrier concentration generating due to the structure of therelated art p/n junction light-emitting device and low Mg dopingefficiency of the p-GaN nitride semiconductor itself, and a currentcrowding problem depending on an increase of contact resistanceaccordingly can be overcome.

More particularly, by forming the n-AlInN nitride semiconductor on anupper side, transparent conductive oxide such as ITO having opticaltransmittance of 95% higher can be used as a transparent electrode. Thatis, the transparent electrode for applying a bias voltage to an n-AlInNlayer may include a transparent resistive material or transparentconductive oxide, which can maximize current spreading so as to maximizethe optical output and has a good optical transmittance. ITO, ZnO, RuOx,IrOx, NiO, or Au alloy metal including Ni may be used as such amaterial. It is thus possible to implement the optical output of 50% orhigher compared to the related art p/n junction through the use of thetransparent electrode.

Furthermore, the present invention can lower an operating voltage owingto low contact resistance and can improve the reliability of devicesaccordingly. More particularly, a high output light-emitting deviceusing a flip chip method necessarily requires a low operating voltagewhen being applied with the current of a large area 300 mA or higher. Ifcontact resistance of the light-emitting device itself is relativelyhigh so as to apply the same current, the operating voltage isincreased. Accordingly, heat of 100° C. or higher is generated in thelight-emitting device itself. Heat generated internally has a decisiveinfluence on the reliability.

According to the n/p/n junction light-emitting device in accordance withthe present invention, when the same current is applied due to lowcontact resistance, the device can be driven a relatively low operatingvoltage and heat generating within the device is low. Therefore, alight-emitting device with high reliability can be provided.

Meanwhile, FIG. 2 is a view schematically showing the stack structure ofa nitride semiconductor light-emitting device according to a secondembodiment of the present invention.

The stack structure of the nitride semiconductor light-emitting device21 according to a second embodiment of the present invention shows acase where a super grading n-In_(X)Ga_(1-X)N layer 24 whose energybandgap is controlled by sequentially changing the indium composition isfurther formed on the n-AlInN layer 16, when compared with the nitridesemiconductor light-emitting device 1 shown in FIG. 1. At this time, thesuper grading n-In_(X)Ga_(1-X)N layer 24 can be formed to have thecomposition of 0<X<0.2. At this time, the super gradingn-In_(X)Ga_(1-X)N layer 24 may be doped with silicon.

A nitride semiconductor light-emitting device 21 having this stackstructure can be considered as an n/n/p/n junction light-emittingdevice. Further, in the nitride semiconductor light-emitting device 21having this stack structure, a transparent electrode for applying a biasvoltage can be formed in the super grading n-In_(X)Ga_(1-X)N layer 24.

Furthermore, though not shown in the drawing, an InGaN/AlInGaN supperlattice structure layer or an InGaN/InGaN supper lattice structure layercan be formed on the n-AlInN layer 16 instead of the super gradingn-In_(X)Ga_(1-X)N layer 24. In this case, the InGaN/AlInGaN supperlattice structure layer or the InGaN/InGaN supper lattice structurelayer may be doped with silicon.

The structure of an active layer adopted in a nitride semiconductorlight-emitting device 31 according to the present invention will bedescribed in more detail with reference to FIG. 3. FIG. 3 is a viewschematically showing the stack structure of a nitride semiconductorlight-emitting device according to a third embodiment of the presentinvention. The layers (the same reference numerals given), which havebeen described with reference to FIG. 1, of the stack structure shown inFIG. 3, will not be described.

In the nitride semiconductor light-emitting device 31 according to athird embodiment of the present invention, a low-mole In_(X)Ga_(1-X)Nlayer 10 having a low content of indium that controls the strain of theactive layer is formed in order to increase internal quantum efficiency,as shown in FIG. 3. Furthermore, in order to improve the optical outputand reverse leakage current due to indium fluctuation, SiN_(X) clusterlayers 33, 35, which are controlled in atomic scale form, are furtherformed on top and bottom surfaces of the low-mole In_(X)Ga_(1-X)N layer10, respectively.

Furthermore, the active layer that emits light can have a single quantumwell structure or a multiple quantum well structure formed of anIn_(Y)Ga_(1-Y)N well layer/In_(Z)Ga_(1-Z)N barrier layer.

FIG. 3 shows an example of the light-emitting device having a multiplequantum well structure in which SiN_(X)cluster layers 39, 45 are furtherprovided between In_(Y)Ga_(1-Y)N well layers 37, 43 and In_(Z)Ga_(1-Z)Nbarrier layers 41, 47 as the active layers. In this case, in order toimprove light-emitting efficiency of the active layer, the compositionratio can be controlled to In_(Y)Ga_(1-Y)N well layer (0<y<0.35)/SiN_(X)cluster layer/In_(Z)Ga_(1-Z)N barrier layer (0<z<0.1). Further, whenconsidering the relation with the low-mole In_(X)Ga_(1-X)N layer 10having a low content of indium, the content of indium doped into theIn_(Y)Ga_(1-Y)N well layers 37, 43, the content of indium doped into theIn_(Z)Ga_(1-Z)N barrier layers 41, 47, and the content of indium dopedinto the low-mole In_(X)Ga_(1-X)N layer 10 can be controlled to have thevalues of 0<x<0.1, 0<y<0.35 and 0<z<0.1, respectively.

Furthermore, though not shown in the drawing, a GaN cap layer thatcontrols the amount of indium fluctuation in the In_(Y)Ga_(1-Y)N welllayer can be further formed between the In_(Y)Ga_(1-Y)N well layer andthe InZGa_(1-Z)N barrier layer, which form the active layers. At thistime, the contents of indium of the well layer and the barrier layerthat emit light can be constructed using In_(Y)Ga_(1-Y)N(0<y<0.35)/GaNcap/In_(Z)Ga_(1-Z)N(0<z<0.1).

Furthermore, after the last layer of the active layer, which has asingle quantum well structure or a multiple quantum well structure, isgrown, a SiN_(X) cluster layer 140 is grown to a thickness of atomicscale, so that internal diffusion of the active layer within Mg atoms ofthe p-GaN layer 100 can be prohibited.

Meanwhile, FIG. 4 is a view schematically showing the stack structure ofa nitride semiconductor light-emitting device according to a fourthembodiment of the present invention. The layers (the same referencenumerals given), which have been described with reference to FIG. 1, ofthe stack structure shown in FIG. 4, will not be described.

A nitride semiconductor light-emitting device 51 according to a fourthembodiment of the present invention further includes a super gradingn-In_(X)Ga_(1-X)N layer 52 whose energy bandgap is controlled bysequentially changing the indium composition is further formed on thep-GaN layer 14. Furthermore, FIG. 4 shows a case where an n-AlInN layer54 is further formed on the super grading n-In_(X)Ga_(1-X)N layer 52.

The nitride semiconductor light-emitting device 51 having this stackstructure can be interpreted as an n/n/p/n junction light-emittingdevice. Further, in the nitride semiconductor light-emitting device 51having this stack structure, a transparent electrode for applying a biasvoltage may be formed in the n-AlInN layer 54.

Meanwhile, although FIG. 4 shows a case where the super gradingn-In_(X)Ga_(1-X)N layer 52 is formed on the p-GaN layer 15, anInGaN/AlInGaN supper lattice structure layer or an InGaN/InGaN supperlattice structure may be formed on the p-GaN layer 15 instead of thesuper grading n-In_(X)Ga_(1-X)N layer 52.

Furthermore, FIG. 5 is a view schematically showing the stack structureof a nitride semiconductor light-emitting device according to a fifthembodiment of the present invention. The layers (the same referencenumerals given), which have been described with reference to FIG. 1, ofthe stack structure shown in FIG. 5, will not be described.

A nitride semiconductor light-emitting device 61 according to a fifthembodiment of the present invention is characterized in that a p-AlInNlayer 66 is formed on the p-GaN layer 16. In this case, the p-AlInNlayer 66 may be doped with magnesium.

The nitride semiconductor light-emitting device 61 having this stackstructure can be interpreted as a p/n junction light-emitting device,but can provide light-emitting efficiency similar to other embodimentsby way of a physical characteristic of the p-AlInN layer 66. Further, inthe nitride semiconductor light-emitting device 61 having this stackstructure, a transparent electrode for applying a bias voltage may beformed in the p-AlInN layer 66.

Further, FIG. 6 is a view schematically showing the stack structure of anitride semiconductor light-emitting device according to a sixthembodiment of the present invention.

The stack structure of a nitride semiconductor light-emitting device 71according to a sixth embodiment of the present invention shows a casewhere a super grading n-In_(X)Ga_(1-X)N layer 74 whose energy bandgap iscontrolled by sequentially changing the indium composition is furtherformed on the p-AlInN layer 66, when compared with the nitridesemiconductor light-emitting device 61 shown in FIG. 5. At this time,the super grading n-In_(X)Ga_(1-X)N layer 74 may be formed to have thecomposition of 0<x<0.2. At this time, the super gradingn-In_(X)Ga_(1-X)N layer 74 may be doped with silicon.

A nitride semiconductor light-emitting device 71 having this stackstructure can be considered as an n/p/p/n junction light-emittingdevice. Further, in the nitride semiconductor light-emitting device 71having this stack structure, a transparent electrode for applying a biasvoltage may be formed in the super grading n-In_(X)Ga_(1-X)N layer 74.

Furthermore, though not shown in the drawing, an InGaN/AlInGaN supperlattice structure layer or an InGaN/InGaN supper lattice structure layermay be formed on the n-AlInN layer 66 instead of the super gradingn-In_(X)Ga_(1-X)N layer 74. In this case, the InGaN/AlInGaN supperlattice structure layer or the InGaN/InGaN supper lattice structurelayer may be doped with silicon.

Meanwhile, FIG. 7 is a view schematically showing the stack structure ofa nitride semiconductor light-emitting device according to a seventhembodiment of the present invention.

A nitride semiconductor light-emitting device 81 according to thepresent invention includes a buffer layer 84 formed on the substrate 82,as shown in FIG. 7. In this case, the buffer layer 84 may have anAlInN/GaN stack structure, an InGaN/GaN supper lattice structure, anIn_(X)Ga_(1-X)N/GaN stack structure or the stack structure ofAl_(X)In_(Y)Ga_(1-(X+Y))N/In_(X)Ga_(1-X)N/GaN.

Further, an In-doped GaN layer 86 into which indium is doped is formedon the buffer layer 84. A n-type first electrode layer is formed on theIn-doped GaN layer 86. In this case, a Si—In co-doped GaN layer 88 intowhich silicon and indium are doped at the same time can be adopted asthe n-type first electrode layer.

Furthermore, an n-AlInN cladding layer 90 is formed on the Si-Inco-doped GaN layer 88. An n-InGaN layer 92 is formed on the n-AlInNcladding layer 90. An active layer 94 that emits light is also formed onthe n-InGaN layer 92. The active layer 94 may have a single quantum wellstructure or a multiple quantum well structure. An example of the stackstructure constituting the active layer 94 will be described in moredetail later on with reference to FIG. 9. In addition, according to theactive layer 94 in accordance with the present invention, there is anadvantage in that sufficient optical efficiency can be accomplished eventhe active layer 94 has a single quantum well structure.

Thereafter, a p-InGaN layer 96 is formed on the active layer 94. Ap-AlInN cladding layer 98 is formed on the p-InGaN layer 96.Furthermore, a p-GaN layer 100 is formed on the p-AlInN cladding layer98. At this time, the p-GaN layer 100 may be doped with magnesium (Mg).

In addition, an n-type second electrode layer is formed on the p-GaNlayer 100. In this case, a super grading n-In_(X)Ga_(1-X)N layer 102whose energy bandgap is controlled by sequentially changing the indiumcomposition can be adopted as the n-type second electrode layer. At thistime, the composition of the super grading n-In_(X)Ga_(1-X)N layer 102can be controlled to 0<x<0.2. Further, the super gradingn-In_(X)Ga_(1-X)N layer 102 may doped with silicon.

As described above, in the nitride semiconductor light-emitting deviceaccording to the present invention, both the first electrode layer 88and the second electrode layer 102 are formed using an n-type nitridesemiconductor and the p-GaN layer 100 is formed therebetween. Therefore,in view of the above structure, it can be considered that the nitridesemiconductor light-emitting device of the present invention has an npnjunction light-emitting device structure unlike the related art pnjunction light-emitting device.

Furthermore, the n-type nitride semiconductor (e.g., the super gradingn-In_(X)Ga_(1-X)N layer 102), which is used as the second electrodelayer, has resistance lower than that of an existing p-GaN contactlayer. Thus, contact resistance can be reduced and current implantationcan be maximized. In addition, a transparent electrode for applying abias voltage to the second electrode layer can include a transparentresistive material or transparent conductive oxide, which can maximizecurrent dispersing so as to maximize the optical output and have a goodoptical transmittance. ITO, ZnO, RuOx, IrOx, NiO, or Au alloy metalincluding Ni may be used as such a material.

In this case, though not shown in the drawing, the second electrodelayer may have an InGaN/AlInGaN supper lattice structure layer or anInGaN/InGaN supper lattice structure layer. Further, the InGaN/AlInGaNsupper lattice structure layer or the InGaN/InGaN supper latticestructure layer may be doped with silicon.

Furthermore, though not shown in the drawing, an n-AlInN layer may beused as the second electrode layer.

According to the nitride semiconductor light-emitting device 81constructed above in accordance with the present invention, the n-AlInNcladding layer 90 and the p-AlInN cladding layer 98 are insertedlower/upper side to the active layers 94, respectively. Therefore,internal quantum efficiency can be improved by prohibiting carrierimplantation efficiency within the active layer 94 and current overflow.

Further, FIG. 8 is a view schematically showing the stack structure of anitride semiconductor light-emitting device according to an eighthembodiment of the present invention. The layers (the same referencenumerals given), which have been described with reference to FIG. 7, ofthe stack structure shown in FIG. 8, will not be described.

The nitride semiconductor light-emitting device 111 according to aneighth embodiment of the present invention is different from the nitridesemiconductor light-emitting device 81 shown in FIG. 7 according to theseventh embodiment in that an In_(X)Ga_(1-X)N layer 114 having a lowcontent of indium.

That is, according to the nitride semiconductor light-emitting device111 in accordance with an eighth embodiment of the present invention,the In_(X)Ga_(1-X)N layer 114 having a low content of indium is furtherformed between the n-InGaN layer 92 and the active layer 94. The reasonis that in order to increase internal quantum efficiency, theIn_(X)Ga_(1-X)N layer 114 having a low content of indium is furtherformed so that it can control the strain of the active layer 94.

The structure of an active layer adopted in a nitride semiconductorlight-emitting device 121 according to the present invention will bedescribed in more detail with reference to FIG. 9. FIG. 9 is a viewschematically showing the stack structure of a nitride semiconductorlight-emitting device according to an ninth embodiment of the presentinvention. The layers (the same reference numerals given), which havebeen described with reference to FIG. 7, of the stack structure shown inFIG. 9, will not be described.

The nitride semiconductor light-emitting device 121 according to a ninthembodiment of the present invention includes a low-mole In_(X)Ga_(1-X)Nlayer 122 having a low content of indium, which controls the strain ofthe active layer, in order to increase internal quantum efficiency, asshown in FIG. 9. Furthermore, in order to improve the optical output andreverse leakage current due to indium fluctuation, SiN_(X) clusterlayers 132, 134, which are controlled in atomic scale form, are furtherformed on top and bottom surfaces of the low-mole In_(X)Ga_(1-X)N layer122.

Furthermore, the active layer that emits light may have a single quantumwell structure or a multiple quantum well structure formed using anIn_(Y)Ga_(1-Y)N well layer/In_(Z)Ga_(1-Z)N barrier layer.

FIG. 9 shows an example of the light-emitting device having a multiplequantum well structure in which SiN_(X) cluster layers 136, 138 arefurther provided between In_(Y)Ga_(1-Y)N well layers 124, 128 andIn_(Z)Ga_(1-Z)N barrier layers 126, 130 as the active layers. In thiscase, in order to improve emission efficiency of the active layer, thecomposition ratio may be controled to In_(Y)Ga_(1-Y)N well layer(0<y<0.35)/SiN_(X) cluster layer/In_(Z)Ga_(1-Z)N barrier layer(0<z<0.1). Further, when considering the relation with the low-moleIn_(X)Ga_(1-X)N layer 122 having a low content of indium, the content ofindium doped into the In_(Y)Ga_(1-Y)N well layers 124, 128, the contentof indium doped into the In_(Z)Ga_(1-Z)N barrier layers 126, 130 and thecontent of indium doped into the low-mole In_(X)Ga_(1-X)N layer 122 maybe controlled to have 0<x<0.1, 0<y<0.35 and 0<z<0.1, respectively.

Furthermore, though not shown in the drawing, a GaN cap layer thatcontrols the amount of indium fluctuation in the In_(Y)Ga_(1-Y)N welllayer may be further formed between the In_(Y)Ga_(1-Y)N well layer andthe In_(Ga) _(1-Z)N barrier layer, which form the active layers. At thistime, the content of indium of each of the well layer and the barrierlayer that emit light may be constructed using In_(Y)Ga_(1-Y)N(0<y<0.35)/GaN cap/In_(Z)Ga_(1-Z)N (0<z<0.1).

Furthermore, after the last layer of the active layer, which has asingle quantum well structure or a multiple quantum well structure, isgrown, a SiN_(X) cluster layer 140 is grown to a thickness of atomicscale, so that internal diffusion of the active layer within Mg atoms ofthe p-GaN layer 100 can be prohibited.

Meanwhile, FIG. 10 is a view schematically showing the stack structureof a nitride semiconductor light-emitting device according to a tenthembodiment of the present invention. The layers (the same referencenumerals given), which have been described with reference to FIG. 7, ofthe stack structure shown in FIG. 10, will not be described.

A nitride semiconductor light-emitting device 141 according to a tenthembodiment of the present invention includes an active layer 94 formedon an n-AlInN cladding layer 90 and a p-AlInN cladding layer 98 formedon the active layer 94.

That is, the nitride semiconductor light-emitting device 141 accordingto a tenth embodiment of the present invention has a modified stackstructure in which the n-InGaN layer 92 and the p-InGaN layer 96 are notformed when compared with the nitride semiconductor light-emittingdevice 81 according to a seventh embodiment shown in FIG. 7.

Further, FIG. 11 is a view schematically showing the stack structure ofa nitride semiconductor light-emitting device according to an eleventhembodiment of the present invention. The layers (the same referencenumerals given), which have been described with reference to FIG. 7, ofthe stack structure shown in FIG. 11, will not be described.

A nitride semiconductor light-emitting device 151 according to aneleventh embodiment of the present invention includes an active layer 94formed on a Si—In co-doped GaN layer 88 (i.e., a first electrode layer),and a p-InGaN layer 96 and a p-AlInN cladding layer 98 both of which areformed on the active layer 94.

That is, the nitride semiconductor light-emitting device 151 accordingto a eleventh embodiment of the present invention has a modified stackstructure in which the n-AlInN cladding layer 90 and the n-InGaN layer92 are not formed when compared with the nitride semiconductorlight-emitting device 81 according to a seventh embodiment shown in FIG.7.

INDUSTRIAL APPLICABLILITY

According to a nitride semiconductor light-emitting device andfabricating method thereof in accordance with the present invention,there are advantages in that the crystallinity of an active layerconstituting a nitride semiconductor light-emitting device can beimproved and the optical output and reliability can be improved.

1. A nitride semiconductor light-emitting device, comprising: a firstnitride semiconductor layer; an active layer formed on the first nitridesemiconductor layer; a second nitride semiconductor layer formed on theactive layer; and a third nitride semiconductor layer having AlIn, whichis formed on the second nitride semiconductor layer
 2. The nitridesemiconductor light-emitting device as claimed in claim 1, wherein asubstrate, and a buffer layer formed on the substrate are further formedunder the first nitride semiconductor layer.
 3. The nitridesemiconductor light-emitting device as claimed in claim 1, wherein thefirst nitride semiconductor layer comprises: a GaN based layer intowhich In is doped or not doped; a first electrode layer formed on theGaN based layer; and an In_(X)Ga_(1-X)N layer formed on the firstelectrode layer.
 4. The nitride semiconductor light-emitting device asclaimed in claim 2, wherein the buffer layer has one of an AlInN/GaNstack structure, an InGaN/GaN supper lattice structure, anIn_(X)Ga_(1-X)N/GaN stack structure and a stack structure of anAl_(X)In_(Y)Ga_(1-(X+Y))N/In_(X)Ga_(1-X)N/GaN.
 5. The nitridesemiconductor light-emitting device as claimed in claim 3, wherein thefirst electrode layer is a GaN based layer into which silicon and indiumare doped at the same time.
 6. The nitride semiconductor light-emittingdevice as claimed in claim 1, wherein a first SiN_(X) cluster layer anda second SiN_(X) cluster layer are further formed on bottom and topsurfaces of the In_(X)Ga_(1-X)N layer, respectively, which is includedin the first nitride semiconductor layer.
 7. The nitride semiconductorlight-emitting device as claimed in claim 6, wherein the first SiN_(X)cluster layer and the second SiN_(X) cluster layer are formed to athickness of atomic scale.
 8. The nitride semiconductor light-emittingdevice as claimed in claim 1, wherein the active layer has a singlequantum well structure or a multiple quantum well structure formed usingan In_(Y)Ga_(1-Y)N well layer/In_(Z)Ga_(1-Z)N barrier layer.
 9. Thenitride semiconductor light-emitting device as claimed in claim 8,further comprising a SiN_(X) cluster layer formed between theIn_(Y)Ga_(1-Y)N well layer and the In_(Z)Ga_(1-Z)N barrier layer formingthe active layer.
 10. The nitride semiconductor light-emitting device asclaimed in claim 8, further comprising a GaN based cap layer formedbetween the In_(Y)Ga_(1-Y)N well layer and the In_(Z)Ga_(1-Z)N barrierlayer forming the active layer.
 11. The nitride semiconductorlight-emitting device as claimed in claim 1, further comprising aSiN_(X) cluster layer formed between the active layer and the secondnitride semiconductor layer.
 12. The nitride semiconductorlight-emitting device as claimed in claim 8, wherein the content ofindium doped into the In_(Y)Ga_(1-Y)N well layer, the content of indiumdoped into the In_(Z)Ga_(1-Z)N barrier layer and the content of indiumdoped into the In_(X)Ga_(1-X)N layer have the values of 0<x<0.1,0<y<0.35 and 0<z<0.1, respectively.
 13. The nitride semiconductorlight-emitting device as claimed in claim 1, wherein the second nitridesemiconductor layer is doped with magnesium.
 14. The nitridesemiconductor light-emitting device as claimed in claim 1, wherein thethird nitride semiconductor layer is doped with silicon or magnesium.15. The nitride semiconductor light-emitting device as claimed in claim1, wherein a fourth nitride semiconductor layer of a super gradingstructure in which the content of indium is sequentially changed or asupper lattice structure including In or Al is further formed on a topsurface of the third nitride semiconductor layer.
 16. The nitridesemiconductor light-emitting device as claimed in claim 15, wherein thesuper grading structure has an In_(X)Ga_(1-X)N layer.
 17. The nitridesemiconductor light-emitting device as claimed in claim 15, wherein thesupper lattice structure is an InGaN/AlInGaN supper lattice structurelayer or an InGaN/InGaN supper lattice structure layer.
 18. The nitridesemiconductor light-emitting device as claimed in claim 15, wherein thefourth nitride semiconductor layer is doped with silicon.
 19. Thenitride semiconductor light-emitting device as claimed in claim 1,wherein a fourth nitride semiconductor layer of a super gradingstructure in which the content of indium is sequentially changed or asupper lattice structure including In or Al is further formed on abottom surface of the third nitride semiconductor layer.
 20. The nitridesemiconductor light-emitting device as claimed in claim 19, wherein thesuper grading structure is an In_(X)Ga_(1-X)N layer (0<x<0.2).
 21. Thenitride semiconductor light-emitting device as claimed in claim 19,wherein the supper lattice structure is an InGaN/AlInGaN supper latticestructure layer or an InGaN/InGaN supper lattice structure layer. 22.The nitride semiconductor light-emitting device as claimed in claim 1,further comprising a transparent electrode formed on the third nitridesemiconductor layer.
 23. The nitride semiconductor light-emitting deviceas claimed in claim 22, wherein the transparent electrode is formedusing transparent conductive oxide or a transparent resistive material.24. The nitride semiconductor light-emitting device as claimed in claim23, wherein the transparent conductive oxide is formed using one of ITO,ZnO, IrOx, RuOx and NiO materials.
 25. The nitride semiconductorlight-emitting device as claimed in claim 23, wherein the transparentresistive material is formed using an Au alloy layer including Ni metal.26. The nitride semiconductor light-emitting device as claimed in claim15, further comprising a transparent electrode formed on the fourthnitride semiconductor layer.
 27. A method of fabricating a nitridesemiconductor light-emitting device, the method comprising: forming abuffer layer on a substrate; forming a GaN based layer on the bufferlayer; forming a first electrode layer on the GaN based layer; formingan In_(X)Ga_(1-X)N layer on the first electrode layer; forming an activelayer on the In_(X)Ga_(1-X)N layer; forming a p-GaN based layer on theactive layer; and forming an n-AlInN layer or a p-AlInN layer on thep-GaN based layer.
 28. The method as claimed in claim 27, furthercomprising the step of forming an n-In_(X)Ga₁₋N layer of a super gradingstructure whose content of indium is sequentially changed or anInGaN/AlInGaN supper lattice structure layer or an InGaN/InGaN supperlattice structure layer on the p-GaN based layer.
 29. The method asclaimed in claim 27, wherein the buffer layer has one of an AlInN/GaNstack structure, an InGaN/GaN supper lattice structure, anIn_(X)Ga_(1-X) N/GaN stack structure and a stack structure of anAl_(X)In_(Y)Ga_(1-(X+Y))N/In_(X)Ga_(1-X)N/GaN.
 30. The method as claimedin claim 27, wherein the first electrode layer is a GaN based layer intowhich silicon and indium are doped at the same time.
 31. The method asclaimed in claim 27, further comprising the step of forming a firstSiN_(X) cluster layer and a second SiN_(X) cluster layer, respectively,prior to and after the step of forming the In_(X)Ga_(1-X)N layer. 32.The method as claimed in claim 27, further comprising the step offorming a SiN_(X) cluster layer between the active layer and the p-GaNbased layer.
 33. The method as claimed in claim 27, further comprisingthe step of forming an n-In_(X)Ga_(1-X)N layer of a super gradingstructure whose content of indium is sequentially changed or anInGaN/AlInGaN supper lattice structure layer or an InGaN/InGaN supperlattice structure layer on the n-AlInN layer or the p-AlInN layer. 34.The method as claimed in claim 27, further comprising the step offorming a transparent electrode on the n-AlInN layer or the p-AlInNlayer.
 35. The method as claimed in claim 33, further comprising thestep of forming a transparent electrode on the super grading structureor the supper lattice structure layer.
 36. A nitride semiconductorlight-emitting device, comprising: a substrate; a buffer layer formingon the substrate; a first GaN based layer into which In is doped, thefirst GaN based layer being formed on the buffer layer; a second GaNbased layer into which Si and In are doped, the second GaN based layerbeing formed on the first GaN based layer; an In_(X)Ga_(1-X)N layerformed on the second GaN based layer; an active layer formed on theIn_(X)Ga_(1-X)N layer; a p-GaN based layer formed on the active layer;and an n-AlInN layer or a p-AlInN layer formed on the p-GaN based layer.37. The nitride semiconductor light-emitting device as claimed in claim36, wherein a nitride semiconductor layer of a super grading structurewhose content of indium is sequentially changed or a supper latticestructure including In or Al is further formed below the n-AlInN layeror p-AlInN layer.
 38. The nitride semiconductor light-emitting device asclaimed in claim 36, wherein a nitride semiconductor layer of a supergrading structure whose content of indium is sequentially changed or asupper lattice structure including In or Al is further formed on then-AlInN layer or p-AlInN layer.
 39. The nitride semiconductorlight-emitting device as claimed in claim 36, further comprising aplurality of SiN_(X) cluster layers formed between the second GaN basedlayer and the p-GaN based layer.
 40. The nitride semiconductorlight-emitting device as claimed in claim 36, further comprising atransparent electrode formed on the n-AlInN layer or p-AlInN layer. 41.The nitride semiconductor light-emitting device as claimed in claim 38,further comprising a transparent electrode formed on the nitridesemiconductor layer of the super grading structure or the supper latticestructure.
 42. A nitride semiconductor light-emitting device,comprising: a first nitride semiconductor layer; an n-AlInN claddinglayer formed on the first nitride semiconductor layer; an n-InGaN layerformed on the n-AlInN cladding layer; an active layer formed on then-InGaN layer; a p-InGaN layer formed on the active layer; a p-AlInNcladding layer formed on the p-InGaN layer; and a second nitridesemiconductor layer formed on the p-AlInN cladding layer.
 43. Thenitride semiconductor light-emitting device as claimed in claim 42,further comprising a second electrode layer formed on the second nitridesemiconductor layer.
 44. The nitride semiconductor light-emitting deviceas claimed in claim 42, wherein a substrate, and a buffer layer formedon the substrate are further formed under the first nitridesemiconductor layer.
 45. The nitride semiconductor light-emitting deviceas claimed in claim 42, wherein the first nitride semiconductor layercomprises an In-doped GaN based layer into which In is doped; and afirst electrode layer formed on the In-doped GaN based layer.
 46. Thenitride semiconductor light-emitting device as claimed in claim 45,wherein the first electrode layer is a GaN based layer into whichsilicon and indium are doped at the same time.
 47. The nitridesemiconductor light-emitting device as claimed in claim 42, furthercomprising an In_(X)Ga_(1-X)N layer formed between the n-InGaN layer andthe active layer.
 48. The nitride semiconductor light-emitting device asclaimed in claim 42, further comprising a plurality of SiN_(X) clusterlayers formed on the first nitride semiconductor layer and the p-AlInNcladding layer.
 49. The nitride semiconductor light-emitting device asclaimed in claim 43, wherein the second electrode layer is a supergrading structure in which the content of indium is sequentially changedor a supper lattice structure including In.
 50. The nitridesemiconductor light-emitting device as claimed in claim 43, wherein thesecond electrode layer is formed using an n-AlInN layer.
 51. The nitridesemiconductor light-emitting device as claimed in claim 43, wherein thesecond electrode layer is doped with silicon.
 52. The nitridesemiconductor light-emitting device as claimed in claim 42, furthercomprising a transparent electrode formed on the second nitridesemiconductor layer.
 53. The nitride semiconductor light-emitting deviceas claimed in claim 43, further comprising a transparent electrodeformed on the second electrode layer.
 54. A nitride semiconductorlight-emitting device, comprising: a first nitride semiconductor layer;an n-AlInN cladding layer formed on the first nitride semiconductorlayer; an active layer formed on the n-AlInN cladding layer; a p-AlInNcladding layer formed on the active layer; and a second nitridesemiconductor layer formed on the p-AlInN cladding layer.
 55. Thenitride semiconductor light-emitting device as claimed in claim 54,further comprising a second electrode layer formed on the second nitridesemiconductor layer.
 56. The nitride semiconductor light-emitting deviceas claimed in claim 54, wherein a substrate, and a buffer layer formedon the substrate are further formed under the first nitridesemiconductor layer.
 57. The nitride semiconductor light-emitting deviceas claimed in claim 54, wherein the first nitride semiconductor layercomprises an In-doped GaN based layer into which In is doped; and afirst electrode layer formed on the In-doped GaN based layer.
 58. Thenitride semiconductor light-emitting device as claimed in claim 57,wherein the first electrode layer is a GaN based layer into whichsilicon and indium are doped at the same time.
 59. The nitridesemiconductor light-emitting device as claimed in claim 54, furthercomprising an In_(X)Ga_(1-X)N layer formed between the n-AlInN claddinglayer and the active layer.
 60. The nitride semiconductor light-emittingdevice as claimed in claim 54, further comprising a plurality of SiN_(X)cluster layers formed on the first nitride semiconductor layer and thep-AlInN cladding layer.
 61. The nitride semiconductor light-emittingdevice as claimed in claim 55, wherein the second electrode layer is asuper grading structure in which the content of indium is sequentiallychanged or a supper lattice structure including In.
 62. The nitridesemiconductor light-emitting device as claimed in claim 55, wherein thesecond electrode layer is formed using an n-AlInN layer.
 63. The nitridesemiconductor light-emitting device as claimed in claim 55, wherein thesecond electrode layer is doped with silicon.
 64. The nitridesemiconductor light-emitting device as claimed in claim 54, furthercomprising a transparent electrode formed on the second nitridesemiconductor layer.
 65. The nitride semiconductor light-emitting deviceas claimed in claim 55, further comprising a transparent electrodeformed on the second electrode layer.
 66. The nitride semiconductorlight-emitting device as claimed in claim 54, further comprising ap-InGaN layer formed between the active layer and the p-AlInN claddinglayer.
 67. A nitride semiconductor light-emitting device, comprising: afirst nitride semiconductor layer; an active layer formed on the firstnitride semiconductor layer; a p-InGaN layer formed on the active layer;a p-AlInN cladding layer formed on the p-InGaN layer; and a secondnitride semiconductor layer formed on the p-AlInN cladding layer. 68.The nitride semiconductor light-emitting device as claimed in claim 67,further comprising a second electrode layer formed on the second nitridesemiconductor layer.
 69. The nitride semiconductor light-emitting deviceas claimed in claim 67, wherein a substrate, and a buffer layer formedon the substrate are further formed under the first nitridesemiconductor layer.
 70. The nitride semiconductor light-emitting deviceas claimed in claim 67, wherein the first nitride semiconductor layercomprises an In-doped GaN based layer into which In is doped; and afirst electrode layer formed on the In-doped GaN based layer.
 71. Thenitride semiconductor light-emitting device as claimed in claim 70,wherein the first electrode layer is a GaN based layer into whichsilicon and indium are doped at the same time.
 72. The nitridesemiconductor light-emitting device as claimed in claim 67, furthercomprising an In_(X)Ga_(1-X)N layer formed between the first electrodelayer and the active layer.
 73. The nitride semiconductor light-emittingdevice as claimed in claim 67, further comprising a plurality of SiN_(X)cluster layers formed on the first nitride semiconductor layer and thep-AlInN cladding layer.
 74. The nitride semiconductor light-emittingdevice as claimed in claim 68, wherein the second electrode layer is asuper grading structure in which the content of indium is sequentiallychanged or a supper lattice structure including In.
 75. The nitridesemiconductor light-emitting device as claimed in claim 68, wherein thesecond electrode layer is formed using an n-AlInN layer.
 76. The nitridesemiconductor light-emitting device as claimed in claim 68, wherein thesecond electrode layer is doped with silicon.
 77. The nitridesemiconductor light-emitting device as claimed in claim 67, furthercomprising a transparent electrode formed on the second nitridesemiconductor layer.
 78. The nitride semiconductor light-emitting deviceas claimed in claim 68, further comprising a transparent electrodeformed on the second electrode layer.
 79. A method of fabricating anitride semiconductor light-emitting device, the method comprising:forming a buffer layer on a substrate; forming an In-doped GaN basedlayer into which indium (In) is doped on the buffer layer; forming afirst electrode layer on the In-doped GaN based layer; forming ann-AlInN cladding layer on the first electrode layer; forming an activelayer on the n-AlInN cladding layer; forming a p-AlInN cladding layer onthe active layer; forming a p-GaN based layer on the p-AlInN claddinglayer; and forming a second electrode layer on the p-GaN based layer.80. The method as claimed in claim 79, wherein the first electrode layeris a GaN based layer into which silicon and indium are doped at the sametime.
 81. The method as claimed in claim 79, further comprising the stepof forming an n-InGaN layer between the n-AlInN cladding layer and theactive layer.
 82. The method as claimed in claim 81, further comprisingthe step of forming an In_(X)Ga_(1-X)N layer between the n-InGaN layerand the active layer.
 83. The method as claimed in claim 79, furthercomprising the step of forming an In_(X)Ga_(1-X)N layer between then-AlInN cladding layer and the active layer.
 84. The method as claimedin claim 83, further comprising the step of forming a plurality ofSiN_(X) cluster layers under surface of the In_(X)Ga_(1-X)N layer andbetween the In_(X)Ga_(1-X)N layer and the p-AlInN cladding layer. 85.The method as claimed in claim 79, wherein the second electrode layer isone of an n-In_(X)Ga_(1-X)N layer of a super grading structure in whichthe content of indium is sequentially changed, an InGaN/InGaN supperlattice structure layer, an InGaN/AlInGaN supper lattice structure layerand an n-AlInN layer.
 86. The method as claimed in claim 79, furthercomprising the step of forming a p-InGaN layer between the active layerand the p-AlInN cladding layer.
 87. The method as claimed in claim 79,further comprising the step of forming a transparent electrode in thesecond electrode layer.
 88. A method of fabricating a nitridesemiconductor light-emitting device, the method comprising: forming abuffer layer on a substrate; forming an In-doped GaN based layer intowhich indium (In) is doped on the buffer layer; forming a firstelectrode layer on the In-doped GaN based layer; forming an active layerthat emits light on the first electrode layer; forming a p-InGaN layeron the active layer; forming a p-AlInN cladding layer on the p-InGaNlayer; forming a p-GaN based layer on the p-AlInN cladding layer; andforming a second electrode layer on the p-GaN based layer.
 89. Themethod as claimed in claim 88, wherein the first electrode layer is aGaN based layer into which silicon and indium are doped at the sametime.
 90. The method as claimed in claim 88, further comprising the stepof forming an In_(X)Ga_(1-X)N layer between the first electrode layerand the active layer.
 91. The method as claimed in claim 90, furthercomprising the step of forming a plurality of SiN_(X) cluster layersunder surface of the In_(X)Ga_(1-X)N layer and between theIn_(X)Ga_(1-X)N layer and the p-AlInN cladding layer.
 92. The method asclaimed in claim 88, wherein the second electrode layer is one of ann-In_(X)Ga_(1-X)N layer of a super grading structure in which thecontent of indium is sequentially changed, an InGaN/InGaN supper latticestructure layer, an InGaN/AlInGaN supper lattice structure layer and ann-AlInN layer.
 93. The method as claimed in claim 88, further comprisingthe step of forming a p-InGaN layer between the active layer and thep-AlInN cladding layer.
 94. The method as claimed in claim 88, furthercomprising the step of forming a transparent electrode in the secondelectrode layer.